Burner and combustion device comprising said burner

ABSTRACT

The burner ( 1 ) according to the invention comprises a main body ( 10 ) provided with an operating cavity ( 11 ) open at least on a first side. The burner also comprises first feed means ( 20 ) arranged to introduce a flow of a first reagent (for example combustion air) into said cavity and second feed means ( 31 ) are arranged to introduce a flow of a second reagent (for example fuel) into the same operating cavity. The first means are configured so as to introduce the first reagent according to a tangential direction, while the second means are configured to introduce the second reagent according to a direction parallel to the direction in which the cavity extends. According to the invention the operating cavity comprises a first portion between the intake position of the first reagent and the intake position of the second reagent. This first portion defines a stabilization chamber of the flow of the first reagent. The operating cavity also comprises a second portion defining a combustion chamber downstream of the intake position of the second reagent.

FIELD OF THE INVENTION

The present invention relates to a burner to be used in general to produce combustion devices having one or more combustion stages. The burner according to the invention can also be used as total burner to generate heat or as partial burner, for example in reforming processes, for generating combustible gases or hydrogen rich gases, or to power fuel cells.

The present invention also relates to a multi-stage combustion device comprising a burner according to the invention.

STATE OF THE ART

As it is known, different types of burners exist and their structure is usually linked to the particular application for which they are destined. Burners can be used to produce complete combustion of a mixture formed by combustion air or fuel or, alternatively, they can be used as a combustion stage within multi-stage combustion devices. Normally, burners can be gaseous fuel (such as methane) or liquid fuel burners according to requirements.

A first type of burner, including for example those normally used in boilers for domestic or industrial use, has the primary objective of heating, through the combustion flame, the fumes that strike coils or heat exchangers inside which a carrier fluid to be heated circulates. More precisely, in these applications, the burners are positioned in combustion chambers inside which the heat exchangers containing the carrier fluid are also positioned. This fluid is therefore heated partly through radiation by the combustion flame and partly through convection by the fumes produced by combustion which lick the outer surface of the heat exchangers.

An example of burners of this type is described in the patent application EP1335163. More precisely, according to this solution, the burner comprises a device called LSV (large scale vortex) used as flame stabilizer. The burner has a structure formed of three concentric pipes. Combustion air is introduced into the innermost pipe and the outermost pipe, while the fuel is introduced into the central pipe in a ratio suitable to create a very lean mixture. The flame develops at the outlet of the central pipe at a widening of the section. The combustion products and excess air subsequently flow into a combustion chamber, on the wall of which there are disposed according to various geometries, and level with the outlet thereof, combustion nozzles for injection of further fuel, having orifices with a particular inclination.

Although being relatively efficient from a functional viewpoint, burners of this type have technical limits deriving above all from the significant dimensions that distinguish their structure. Consequently, they are somewhat unsuitable for those applications in which generation and transmission of high thermal power in small or limited spaces is required, as may be the case, for example, in methane reforming plants or the like.

In these operating conditions “radiant” burners have proved more efficient. More precisely, radiant burners are use in those circumstances where there must be no physical contact between combustion fumes and the material to be heated, thereby producing heat exchange entirely by radiation. From a constructional viewpoint, these burners usually comprise a linear or curved chamber, in which the fumes deriving from combustion circulate. More precisely, these burners are used in those circumstances where there must be no physical contact between combustion fumes and the material to be heated, thereby producing heat exchange entirely by radiation. The fumes deriving from combustion are evacuated directly from the burner and often their enthalpic content is exploited to pre-heat the air in order to increase the performance of the plant. In many solutions of this type the combustion reagents (this expression being intended as indicating the oxidizer and the fuel) are mixed before being introduced into the combustion chamber according to a swirling motion.

The burners of this second type are accompanied by some drawbacks, a first of which is identified in the difficulty in controlling the flow rates. In other words, the composition of the mixture that reaches the combustion area varies continuously. This translates into poor flame stability due to the variable conditions of the mixture. Added to this drawback is the possibility of flash backs, especially in those cases in which the burner does not work in optimal operating conditions. This aspect is particularly critical in terms of safety. Another limit of conventional radiant burners lies in the fact that the radiant walls of the burner are not licked continuously and efficiently by the flame due to its poor stability. This naturally limits the efficiency of the burner as the thermal energy that can be transmitted by the burner through radiation is limited.

On the basis of these considerations, the need emerges for new technical solutions that allow the drawbacks currently accompanying conventional radiant burners to be overcome. Therefore, the main aim of the present invention is to provide a burner that allows the aforesaid limits and drawbacks to be overcome.

Within this aim, a main object is to provide a burner that is functionally versatile, or that can be used for different applications. Another object is to provide a burner of radiant type that allows the transmission of high thermal power deriving from stable and constant combustion. A further object of the present invention is to provide a burner which is compact, reliable and easy to manufacture at competitive costs.

SUMMARY OF THE INVENTION

The present invention relates to a burner comprising a main body provided with a substantially cylindrically shaped cavity which extends along an axial direction and which is open at least on a first side. The burner also comprises first feed means to introduce a flow of a first reagent into the operating cavity in an intake position of the first reagent. These first feed means are configured so as to define a tangential intake of the first reagent into the operating cavity. The burner also comprises second feed means to introduce a flow of a second reagent into said operating cavity in an intake position of said second reagent. Said second feed means are configured so as to introduce the second reagent according to a direction parallel to the axial direction.

According to the invention, the operating cavity comprises a first portion between the intake position of the first reagent and the intake position of the second reagent. This first portion defines a stabilization chamber of the first reagent. The operating cavity also comprises a second portion that configures a combustion chamber downstream of the intake position of the second reagent or downstream of the stabilization chamber with respect to the direction in which the flow of second reagent extends. According to a preferred embodiment of the invention, the burner comprises combustion ignition means which are operatively positioned inside the operating cavity to ignite combustion between the two reagents.

For the purposes of the present invention, the expression reagents is intended as indicating the oxidizer and the fuel that generate combustion. Therefore, in a first possible application of the burner, the flow of first reagent can be a flow of oxidizer, while the flow of second reagent will be a flow of fuel. In a second application the nature of the reagents can be inverted with respect to the previous case and more precisely the first flow of reagent will correspond to a flow of fuel, while the second flow of reagent can be a flow of oxidizer.

It has been found that the presence of a stabilization chamber for flow of the first reagent allows flame conditions that are extremely stable and constant in time to be achieved. In fact, the distance between the intake positions for the two reagents allows precise adjustment of the flow rates, or a constant combustion stoichiometric ratio.

From an operational viewpoint, the reagent that acts as oxidizer for combustion can be air or alternatively a mixture of gases. Analogously, the reagent that acts as fuel can be formed by a flow of combustible gas or, alternatively can be a liquid fuel.

According to a further aspect of the present invention, the first portion of the operating cavity, which defines the stabilization chamber for the first reagent, has the same dimension of diameter as the second portion which defines the combustion chamber. It has been found that this solution allows optimization of the heating conditions of the walls delimiting the combustion chamber, or optimization of the radiation effect that can be obtained through these walls.

According to a further aspect of the present invention, the burner comprises a lance for introducing the flow of second reagent. This lance comprises a portion outside the main body of the burner and a portion inside this main body which extends parallel to the axial direction in which the operating cavity extends. The position of the lance in substance defines the length of the first portion of the operating cavity, or the extension of the stabilization chamber. This extension can be adjusted if necessary, through appropriate means for adjustment of the axial position, as a function of the type of reagents used and as a function of the mass flows thereof in order to optimize combustion.

According to another aspect of the present invention, the combustion ignition means are advantageously positioned inside the lance for intake of the second reagent. This solution is particularly advantageous as the ignition means in fact remain confined in an inert position from a fluid dynamic viewpoint, or in a position that does not obstruct on the one hand stabilization of the flow of the first reagent and on the other propagation of the flame.

The present invention also relates to a combustion device that is characterized in that it comprises a burner according to the present invention. According to a possible embodiment, the combustion device according to the invention comprises a first combustion stage defined by a burner according to the present invention and a second combustion stage defined by a further combustion chamber into which the combustion products produced by the burner flow. Preferably, the combustion device comprises further feed means to introduce a flow of oxidizer into said further combustion chamber.

LIST OF FIGURES

Further features and advantages of the present invention shall be apparent from the description of particular embodiments of the present invention illustrated by way of non-limiting example in the accompanying drawings, wherein:

FIG. 1 is a perspective view of a first embodiment of a burner according to the present invention;

FIGS. 2 and 3 are respectively a front view and a side view of the single-stage burner of FIG. 1;

FIG. 4 is a sectional view according to the line IV-IV of FIG. 1;

FIG. 5 is a perspective view of a second embodiment of a burner according to the present invention;

FIG. 6 is a side view of the burner of FIG. 5;

FIG. 7 is a longitudinal sectional view of the burner of FIG. 5;

FIG. 8 is a perspective view of a combustion device with two combustion stages comprising the burner of FIG. 1;

FIG. 9 is a longitudinal sectional view of the device of FIG. 8;

FIG. 10 is a perspective view of a further combustion device with two combustion stages comprising the burner of FIG. 5;

FIG. 11 is a side view of the combustion device of FIG. 8.

DETAILED DESCRIPTION

With reference to the aforesaid figures, the burner 1 according to the invention comprises a main body comprising a substantially cylindrically shaped operating cavity 11 which extends according to an axial direction X. The operating cavity 11 is open at least on a first side so as to be in communication with the environment outside the main body. More precisely, in the case illustrated the operating cavity 11 is delimited on a second side thereof, opposite the first, by a housing wall 12.

The burner 1 according to the invention comprises first combustion feed means to introduce a flow of a first reagent into the operating cavity 11 in an intake position of said first reagent (indicated with the reference P1 and hereafter also with the expression “first position P1”). More precisely, the first feed means are structured so as to configure a tangential intake of the flow of first reagent in the operating cavity 11. In other words, they configure a flow for the first reagent which enters the cavity 11 according to a direction tangent to the cross section of this cavity.

The burner 1 also comprises second feed means configured to introduce a flow of second reagent C into the operating cavity 11 in an intake position of said second reagent (indicated with the reference P2 and hereafter also with the expression “second position P2”). More precisely, these second feed means configure an axial flow of fuel inside the operating cavity 11.

According to the invention, the operating cavity 11 comprises a first portion 11A, between the intake position P1 of said first reagent AC and the intake position P2 of said second reagent. This first portion 11A forms a stabilization chamber of the first reagent introduced through the first feed means. The operating cavity 11 also comprises a second portion 11B, in communication with the first portion 11A, which defines a combustion chamber downstream of the intake position P2 of the second reagent with respect to the axial direction of flow of this second reagent. For the purposes of the description, the expression “stabilization chamber 11A” will be used to indicate the first portion 11A, and the expression “combustion chamber 11B” will be used to indicate the second portion 11B.

FIGS. 1 to 4 relate to an embodiment of a burner in which the first reagent is combustion air and the second reaction is gaseous fuel such as methane. Hereafter, purely to simplify the description, the reagent that acts as “oxidizer” will always be considered as first reagent and the one that acts as “fuel” as second reagent“. However, the scope of the invention also includes the possibility of inverting the intake position of the fuel and of the oxidizer in the operating cavity 11. From an operating viewpoint, the burner 1 can also use a flow of air or, alternatively, a gaseous mixture, as oxidizer. Either gaseous fuel or liquid fuel can instead be used as fuel.

With reference, for example, to the sectional view of FIG. 4, the main body is formed of a tubular element 10 which extends along an axial direction X with an operating cavity 11 which extends substantially for the entire length thereof. The tubular element 10 can be made of steel, copper or other metal material according to the type of application for which the burner 1 is destined. The use of a tubular element 10 of this type has proved to be particularly useful as it allows the burner 1 to be advantageously used as linear radiant element. The heat generated by combustion can be transferred radially through the walls of the tubular element 10 to a mass (fluid, gaseous liquid or solid) arranged around this tubular element. In a first possible application, for example, the heat can be transferred through the tubular element 10 to a fluid mass that licks the outside of the element. In a second possible application, the heat can be transferred, through the walls of the tubular element 10, to a solid metal mass usable, for example, as thermal wheel in an evaporator. In a further application, the heat can be transferred by conduction to a heat exchanger welded to the outer surface of the tubular element 10.

Again with reference to FIG. 4, purely to simplify the description, the operating cavity 11 preferably has a constant diameter for the entire length thereof. In other words, the stabilization chamber 11A and the combustion chamber 11B have the same diametric extension. It has been found that this solution advantageously stabilizes the combustion flame while simultaneously allowing it to adhere uniformly to the walls, permitting more effective and uniform heating of the walls of the tubular element 10. Simultaneously, the constant section along the longitudinal axis X defines for the burner 1 a particularly compact configuration and therefore adaptable to different types of application. In other words, the linear shape of the burner advantageously increases the number of possible spheres of application.

Again with reference to the sectional view of FIG. 4, the housing wall 12 delimiting the operating cavity 11 is defined by a cap element 13 connected permanently to one end of the tubular element 10. In the solution illustrated the first feed means comprise a feed duct 20, connected to the tubular element 10, which is in communication on the one side with a source (not shown in the figures) from which the flow of first reagent, in this case combustion air AC, derives. This source could comprise, for example, a blower or alternatively a compressed air duct or any other system capable of providing the flow rate of combustion air AC required at the pressure necessary to overcome the load losses and thus allow correct operation of the burner 1.

The feed duct 20 is in communication on the opposite side with the operating cavity 11 through an opening 8 whose position in substance defines the intake position P1 of the flow of combustion air AC (first reagent) into the cavity or into the stabilization chamber 11 defined thereby. As illustrated, the position of the opening 8 is substantially adjacent to the housing wall 12 so as to oblige the entire flow of combustion air to move in the direction of the combustion chamber 11B. In the case illustrated in FIGS. 1 to 4, the feed duct 20 extends according to a direction parallel to that of the longitudinal axis, but could also extend according to another direction, for example orthogonally to this longitudinal axis, as shown by the broken line in FIG. 2.

With reference to FIGS. 3 and 4, the second feed means preferably comprise a lance element 30 for intake of the second reagent, which in the case illustrated is defined by gaseous fuel. This lance element 30 extends through the cap element 13 and is preferably connected thereto. More precisely, the lance element 30 is inserted in a hole passing through the cap element 13 so as to emerge with a first portion 30A inside the operating cavity 11. The lance element 30 comprises a second portion 30B outside the tubular element 10. This second portion 30B is in communication, for example through a supply pipe 31, with a fuel source, not shown in the figures, which can, for example, be a bottle of methane or other pressurized gaseous fuel.

As clearly illustrated, the first portion 30A of the lance element 30 is substantially coaxial with the operating cavity 11 and terminates with an emission end 33 through which the fuel C exits. The axial extension of this first portion 30A in practice defines the axial extension of the stabilization chamber as it stabilizes the distance between the intake position P1 of the first reagent (combustion air in the case illustrated) and the intake position P2 of the second reagent (fuel in the case illustrated). It has been found that excellent results in terms of combustion stability are obtained, given the same reagents used, when the ratio between the distance LT of the intake positions (or the distance between the position P1 and the position P2) and the internal diameter D of the stabilization chamber 11A (or of the first portion 11A) is comprised within an interval of values between 1 and 10. It has also been found that optimal results in terms of combustion stability are achieved when the ratio between the length LT of the first portion 11A and the length L of the second portion 11B is comprised within an interval of values between 0.1 and 2. Moreover, it has been found that particularly favorable combustion conditions are achieved when the ratio between internal diameter D of the stabilization chamber and diameter D1 of the first portion 30A of the lance element 30 is contained within an interval of values between 2 and 10.

In the case illustrated in the figures, the combustion ignition means comprise a spark igniter 40 arranged inside the lance element 30. More precisely, the spark igniter 40 comprises a central body 40A, made of insulating material, arranged coaxially inside the lance element 30 and connected by a first part to an electrical source (not shown) through an electrical connection plug 39. The opposite part of the central body 40A comprises an ignition end 40B, also called tip, which emerges with respect to the fuel delivery end 33 of the lance element. This emerging position of the tip allows the spark to strike in a region in which flammable mixture is undoubtedly present.

FIGS. 5 to 7 relate to a second embodiment of the burner 1 according to which it is supplied with liquid fuel. With reference, for example, to FIG. 5, it can be seen that the main body of the burner is also in this case composed of a tubular element 10 made of metal material closed at one end by a cap element delimiting on the one side the operating cavity 11. The first feed means are configured so as to allow tangential intake into the operating cavity 11 of an air flow according to a method substantially analogous to the one provided for in the previous case. With reference to the sectional view of FIG. 7, the second feed means comprise also in this case a central lance 30 which is closed at the end through a closing element 65 which forms a nozzle 66 through which the flow of second reagent (in this case the fuel C) exits substantially in axial direction. The axial position of the nozzle 66 in substance defines the intake position P2 of the second reagent. In particular, the liquid fuel reaches the nozzle 66 through a feed circuit 68 which can also comprise a heater 70 (see, for example, FIG. 6) to take the fuel to the temperature and pressure conditions necessary to make it vaporize, after having passed through the nozzle 66, in the operating cavity 11 of the tubular element 10.

As illustrated in FIG. 7, in this second embodiment of the burner 1 the sparking means are substantially the same as those provided in the case of the burner with gaseous fuel. In particular, in this embodiment, adjustment means 73 are provided to adjust the axial position of the lance 30. More precisely, these means allow adjustment of the depth of insertion of the lance 30 in the operating cavity 11 within a certain interval so as to optimize operation of the lance according to the fuel used. In other words, these adjustment means 73 of the axial position allow, according to the type of reagents, selection of the most suitable position in which to strike the spark.

With reference to FIGS. 8 to 11, the present invention also relates to a combustion device 5 comprising a burner 1 according to the present invention More precisely, it relates to a multi-stage combustion device 5 wherein the first combustion stage is produced through a burner 1 with gaseous or liquid fuel according to the description above. In other words the burner 1 in this application is used to produce partial combustion that will subsequently be completed in the various combustion stages of the device 5. Partial combustion, with respect to total combustion, is achieved by varying the combustion air/fuel ratio substantially without any change to the structure of the burner. The combustion device 5 according to the invention could be used, for example, as first stage of a multi-stage combustion system or alternatively it could be used for hydrocarbon reforming.

FIG. 8 is a perspective view, of a combustion device 5 according to the invention which comprises a gaseous fuel burner. As illustrated, the device 5 comprises a housing liner 50, positioned inside which is at least part of the tubular element 10 defining the operating cavity 11, or the combustion chamber 11A of the burner 1 in which the first combustion stage is produced (hereinafter also indicated as primary combustion chamber 11A). The volume between the housing liner 50 and the part of the burner 1 contained therein defines a second combustion chamber 18 in which the second combustion stage is produced. For this reason, this chamber will also be indicated with the expression secondary combustion chamber 18.

With reference to FIG. 9, the housing liner 50 has a substantially cylindrical shape extending between a first transverse wall 51 and a second transverse wall 52 opposite the first. These walls 51, 52 extend in a substantially transverse manner to the longitudinal direction X defined above. The tubular element 10 of the burner 1 is positioned at least partly inside the housing liner 50 through the first wall 51 so that the primary combustion chamber 11B is substantially coaxial with the housing liner 50 or with the secondary combustion chamber 18. As can be seen, the tubular element 10 is distanced from the second wall 52 so that the combustion products delivered from the primary combustion chamber 11A can be released inside the secondary combustion chamber 18.

The first wall 51 of the housing liner 50 comprises a discharge opening 55 to discharge products deriving from the second combustion. In particular, in the solution illustrated the discharge opening 55 is coaxial with the housing liner 50 or with the tubular element 10 of the burner 1. The combustion device 5 can advantageously comprise a conveying element 58 to convey the products of the second combustion. In the case illustrated, the conveying element 58 comprises a discharge outlet 59 connectable, through a flange element 59B, to an evacuation duct, not shown in the figures. According to requirements, these products can be conveyed to a further combustion stage of the combustion device 5 or inside another device. Alternatively, the combustion products could be released directly into the atmosphere if their temperature is sufficiently low.

FIGS. 10 and 11 relate to a second embodiment of a combustion device 5 according to the position that differs from the previous one through the use of a liquid fuel burner 1. From comparing FIGS. 8 and 9, it can be understood that in the two embodiments of the combustion device 5 the structure thereof is substantially identical with obvious advantages from the viewpoint of manufacturing costs. Naturally, the dimensions of the two devices are established as a function of the type of fuel to be used and of the operating conditions required.

The technical solutions adopted for the burner allow the aims and objects set to be fully achieved. In particular, the burner according to the invention has high functional versatility, which makes it suitable for use in different applications. In particular, it can be used for partial or total combustion or, alternatively, as heating element of heat carrying fluids or solid masses. The structure of the burner according to the invention allows it to be used to produce particularly compact and efficient multistage combustion devices with extremely limited manufacturing costs.

The burner and the combustion device thus conceived are susceptible to numerous modifications and variants, all falling within the scope of the inventive concept; moreover all details can be replaced by other technically equivalent details.

In practice, the materials used and the contingent dimensions and forms can be any, according to requirements and to the state of the art. 

1. A burner for producing a combustion device, said burner comprising: a main body comprising a substantially cylindrically shaped operating cavity which extends along an axial direction, said operating cavity being open at least on a first side, first feed means to introduce a flow of a first reagent into said operating cavity in an intake position of said first reagent, said first feed means configuring a tangential intake of said first reagent in said operating cavity; second feed means to introduce a flow of a second reagent into said operating cavity in an intake position of said second flow, said second feed means introducing said flow of second reagent according to a direction substantially parallel to said axial direction along which said operating cavity extends, wherein said operating cavity comprises a first portion between said intake position of said first reagent and said intake position of said second reagent, said first portion defining a stabilization chamber of the motion of said first reagent, said operating cavity comprising a second portion defining a combustion chamber downstream of said intake position of said second reagent.
 2. The burner according to claim 1, wherein said burner comprises combustion ignition means positioned inside said operating cavity.
 3. The burner according to claim 1, wherein said first reagent is an oxidizer and wherein said second reagent is a fuel.
 4. The burner according to claim 3, wherein said first reagent is combustion air and wherein said second reagent is liquid or gaseous fuel.
 5. The burner according to claim 1, wherein said first reagent is a fuel and wherein said second reagent is an oxidizer.
 6. The burner according to claim 1, wherein said first portion and said second operating portion have the same diametric dimension.
 7. The burner according to claim 1, wherein said intake position of combustible air is substantially adjacent to said housing wall which delimits said operating cavity.
 8. The burner according to claim 1, wherein the ratio between the length of said first portion and the length of said second portion falls within an interval between 0.1 and
 2. 9. The burner according to claims 2, wherein said first feed means comprise a feed duct connected to said main body, said feed duct being in communication on one side with a source of combustion air and on the other with said operating cavity.
 10. The burner according to claim 1, wherein said second feed means comprise a lance for fuel intake which extends through said housing wall of said main body, said lance comprising a portion outside said main body and in communication with a source of fuel and a portion inside said main body and coaxial with said operating cavity.
 11. The burner according to claim 10, wherein said fuel ignition means are arranged inside said lance for fuel intake.
 12. The burner according to claims 1, wherein said main body is formed by a tubular element made of metal material.
 13. A combustion device, comprising a burner, said burner comprising: a main body comprising a substantially cylindrically shaped operating cavity which extends along an axial direction, said operating cavity being open at least on a first side, first feed means to introduce a flow of a first reagent into said operating cavity in an intake position of said first reagent, said first feed means configuring a tangential intake of said first reagent in said operating cavity; and second feed means to introduce a flow of a second reagent into said operating cavity in an intake position of said second flow, said second feed means introducing said flow of second reagent according to a direction substantially parallel to said axial direction along which said operating cavity extends, wherein said operating cavity comprises a first portion between said intake position of said first reagent and said intake position of said second reagent, said first portion defining a stabilization chamber of the motion of said first reagent, said operating cavity comprising a second portion defining a combustion chamber downstream of said intake position of said second reagent.
 14. The combustion device according to claim 13, wherein said device comprises a first combustion stage produced through said burner and a second combustion stage defined by a further combustion chamber into which the combustion products produced by said burner flow, said device comprising further feed means to introduce combustion air into said further combustion chamber.
 15. The combustion device according to claim 14 wherein said further combustion chamber is defined by a housing liner, inside which at least part of said main body of said burner is positioned, said housing liner having a substantially cylindrical shape and extending longitudinally between a first wall and a second wall opposite the first, said burner being positioned, through said first wall, so that said operating cavity of said main body is substantially coaxial with said housing liner.
 16. The combustion device according to claim 15, wherein said first wall of said housing liner comprises a discharge opening to discharge the products deriving from said second combustion.
 17. The combustion device according to claim 16, wherein said discharge opening is coaxial with said housing liner, said device comprising a conveying element to convey the combustion products delivered through said discharge opening. 